linux-kernel - [PATCH v3 06/26] x86/virt/tdx: Prepare to support P-SEAMLDR SEAMCALLs

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Message-ID: <20260123145645.90444-7-chao.gao@intel.com>
Date: Fri, 23 Jan 2026 06:55:14 -0800
From: Chao Gao <chao.gao@...el.com>
To: linux-coco@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org,
	x86@...nel.org
Cc: reinette.chatre@...el.com,
	ira.weiny@...el.com,
	kai.huang@...el.com,
	dan.j.williams@...el.com,
	yilun.xu@...ux.intel.com,
	sagis@...gle.com,
	vannapurve@...gle.com,
	paulmck@...nel.org,
	nik.borisov@...e.com,
	zhenzhong.duan@...el.com,
	seanjc@...gle.com,
	rick.p.edgecombe@...el.com,
	kas@...nel.org,
	dave.hansen@...ux.intel.com,
	vishal.l.verma@...el.com,
	Chao Gao <chao.gao@...el.com>,
	Farrah Chen <farrah.chen@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH v3 06/26] x86/virt/tdx: Prepare to support P-SEAMLDR SEAMCALLs

P-SEAMLDR is another component alongside the TDX module within the
protected SEAM range. P-SEAMLDR can update the TDX module at runtime.
Software can talk with P-SEAMLDR via SEAMCALLs with the bit 63 of RAX
(leaf number) set to 1 (a.k.a P-SEAMLDR SEAMCALLs).

P-SEAMLDR SEAMCALLs differ from SEAMCALLs of the TDX module in terms of
error codes and the handling of the current VMCS.

In preparation for adding support for P-SEAMLDR SEAMCALLs, do the two
following changes to SEAMCALL low-level helpers:

1) Tweak sc_retry() to retry on "lack of entropy" errors reported by
   P-SEAMLDR because it uses a different error code.

2) Add seamldr_err() to log error messages on P-SEAMLDR SEAMCALL failures.

Signed-off-by: Chao Gao <chao.gao@...el.com>
Tested-by: Farrah Chen <farrah.chen@...el.com>
---
Add seamldr_prerr() as a macro to be consistent with existing code. If
maintainers would like to switch these to static inline functions then I
would be happy to add a new patch to convert existing macros to static
inline functions and build on that.

v3:
 - print P-SEAMLDR leaf numbers in hex
 - use %# to print error code [Binbin]
 - mark the is_seamldr_call() call as unlikely [Binbin]
 - remove the function to get the error code for retry from leaf numbers
   [Yilun]
v2:
 - use a macro rather than an inline function for seamldr_err() for
   consistency.
---
 arch/x86/virt/vmx/tdx/seamcall.h | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/arch/x86/virt/vmx/tdx/seamcall.h b/arch/x86/virt/vmx/tdx/seamcall.h
index 0912e03fabfe..256f71d6ca70 100644
--- a/arch/x86/virt/vmx/tdx/seamcall.h
+++ b/arch/x86/virt/vmx/tdx/seamcall.h
@@ -34,15 +34,28 @@ static __always_inline u64 __seamcall_dirty_cache(sc_func_t func, u64 fn,
 	return func(fn, args);
 }
 
+#define SEAMLDR_RND_NO_ENTROPY	0x8000000000030001ULL
+
+#define SEAMLDR_SEAMCALL_MASK	_BITUL(63)
+
+static inline bool is_seamldr_call(u64 fn)
+{
+	return fn & SEAMLDR_SEAMCALL_MASK;
+}
+
 static __always_inline u64 sc_retry(sc_func_t func, u64 fn,
 			   struct tdx_module_args *args)
 {
+	u64 retry_code = TDX_RND_NO_ENTROPY;
 	int retry = RDRAND_RETRY_LOOPS;
 	u64 ret;
 
+	if (unlikely(is_seamldr_call(fn)))
+		retry_code = SEAMLDR_RND_NO_ENTROPY;
+
 	do {
 		ret = func(fn, args);
-	} while (ret == TDX_RND_NO_ENTROPY && --retry);
+	} while (ret == retry_code && --retry);
 
 	return ret;
 }
@@ -68,6 +81,16 @@ static inline void seamcall_err_ret(u64 fn, u64 err,
 			args->r9, args->r10, args->r11);
 }
 
+static inline void seamldr_err(u64 fn, u64 err, struct tdx_module_args *args)
+{
+	/*
+	 * Note: P-SEAMLDR leaf numbers are printed in hex as they have
+	 * bit 63 set, making them hard to read and understand if printed
+	 * in decimal
+	 */
+	pr_err("P-SEAMLDR (%llx) failed: %#016llx\n", fn, err);
+}
+
 static __always_inline int sc_retry_prerr(sc_func_t func,
 					  sc_err_func_t err_func,
 					  u64 fn, struct tdx_module_args *args)
@@ -96,4 +119,7 @@ static __always_inline int sc_retry_prerr(sc_func_t func,
 #define seamcall_prerr_ret(__fn, __args)					\
 	sc_retry_prerr(__seamcall_ret, seamcall_err_ret, (__fn), (__args))
 
+#define seamldr_prerr(__fn, __args)						\
+	sc_retry_prerr(__seamcall, seamldr_err, (__fn), (__args))
+
 #endif
-- 
2.47.3